1. Field of the Invention
The present invention relates to a image forming device and more particularly to the image forming device having a sheet transportation unit for transporting a sheet to be printed on past a print head.
2. Description of the Related Art
There has been known an image forming device having an elongated flat plate (hereinafter referred to as chute) for guiding a sheet to be recorded on. The chute is supported so as to run between a toner fixing device and a pair of rotatable transport rollers. An aperture electrode body and a back electrode with an electrode tip are supported near the center of the chute on opposite sides thereof. The back electrode and aperture electrode are positioned so that the aperture electrode and the electrode tip of the back electrode are separated by a space.
A sheet to be recorded on is transported between the pair of transport rollers by the rotation thereof. The thus transported sheet follows the chute toward the toner fixing device, thereby passing through the space separating the aperture electrode and the tip of the back electrode.
The space separating the aperture electrode and the tip of the back electrode is extremely narrow. Although actual values vary with the voltage applied to the back electrode, the space can be as narrow as 0.5 mm to 1 mm. To accurately feed the sheet through this space, the pair of transport rollers need to be as close to the aperture electrode and the back electrode as possible.
However, other components, such as those required for development processes, also must be positioned near the aperture electrode. This limits how close the pair of transport rollers can be positioned adjacent to the aperture electrode and the back electrode. Conventionally the chute is supported between the thermal fixing device and the pair of transport rollers so as to be substantially parallel to a direction tangential to both transport rollers. Because of this the sheet is unstably transported between the aperture electrode and the back electrode during printing.
Because the toner charged by and discharged from the aperture electrode body does not become fixed when it impinges to the sheet surface, the characters formed from toner on the surface of the sheet might be smudged if scraped against the aperture electrode body. The quality of printed characters can therefore suffer greatly. Additional components such as plate springs can be provided to support and stabilize the posture of the sheet, but adding new components increases costs.